Hyperspectral Diagnostic Imaging of the Cervix
Hyperspectral Diagnostic Imaging of the Cervix
abstract & commentary
Synopsis: Noncontact in vivo fluorescence imaging of the uterine cervix shows promise as an instrument for the detection of the cervical intraepithelial neoplasia.
Source: Parker MF, et al. Journal of Lower Genital Tract Disease 2000;4:119-124.
The current methods used to screen for and diagnose preinvasive cancer of the cervix (pap smear, colposcopy, and biopsy) require multiple office visits and considerable expense. Because all human tissues fluoresce when subjected to ultraviolet (UV) light, it might be possible to develop an instrument that can use the fluorescence emissions of the tissues on the surface of the uterine cervix either to screen for or diagnose cervical intraepithelial neoplasia (CIN).
Parker and colleagues developed a prototype instrument that directs UV light, generated by a mercury vapor lamp, at the cervix. This causes fluorescence of the tissues on the surface of the cervix. The intensity of the fluorescence can be measured using a scanning imager that reads the intensity of the fluorescence from each pixel in the scanned area. Total scan time was approximately 12 seconds for this prototype instrument. Prior to scanning, the cervix was cleansed with 3% acetic acid.
Thirty-five women were included in the analysis; four women with normal Pap smears and 31 women with abnormal Pap smears. Following each fluorescence scan, the patient underwent standard colposcopy with biopsy of abnormal areas. Two pathologists reviewed all biopsies, and only when the pathologists agreed on the diagnosis were the patients included in the study.
The technique, hyperspectral diagnostic imaging (HSDI), was able to discriminate CIN from normal tissues. The prototype machine did have difficulty differentiating squamous epithelium from squamous metaplasia. Because these preliminary results indicate that HSDI might eventually have clinical applications, Parker et al have begun testing a second-generation instrument.
Comment by Kenneth L. Noller, MD
At the present time, I know of at least five different groups that are developing some sort of instrumentation that uses a variety of electronic techniques to identify CIN. Some of the instruments require touching the cervix with a probe whereas others (like the HSDI instrument in this report) use a "no touch" technique. It has been known for some time that normal and abnormal human tissues respond differently when subjected to various external stimuli such as UV light, electrical currents, etc. Perhaps the best example is the difference in the orientation of tissue molecules when subjected to an external magnetic field (MRI).
While none of the five techniques that are being tested is ready for widespread clinical application, the eventual development of a useful technique is almost certain. Whether the technique will be applicable for widespread screening, or as a method to avoid tissue biopsy is a matter for speculation at present. While I do not think an instrument that merely identifies areas to biopsy will be helpful, an instrument that could be used for screening or in place of actual biopsies might find a place in everyday practice. For example, a woman might have a screening scan performed in a few seconds, a report generated in a few more seconds, and if the report is abnormal the actual tissue diagnosis printed out. Thus, in perhaps less than a minute a woman with CIN might be ready for discussion of treatment. We are probably about a decade away from clinical application. It would be wise, however, for clinicians to keep abreast of the literature as it is published for I firmly believe that we will eventually be using more and more of these techniques in everyday practice.
One interesting bit of information was included in this article on which I did not comment. Sixty-two women were initially scanned, but only 35 were included in the report. While there were several reasons for non inclusion, 15 of the 62 women were not included because the two pathologists could not agree on a diagnosis! Often times, we clinicians assume that a pathology diagnosis is the "gold standard." We need to remember that developing a tissue diagnosis is a very subjective process, much like developing a colposcopic impression. While pathology is very good when things are very abnormal it is far less reliable when dealing with the lower end of a spectrum disease such as CIN.
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